The development of IBD is dependent upon the activation of mucosal leukocyte populations and the production of inflammatory mediators. The central hypothesis of this center's research program presumes that leukocytes are activated following induced disruption of the mucosal barrier in conjunction with intrinsic genetically determined abnormalities of regulatory mechanisms. In order to effectively define the mechanisms contributing to IBD, it is essential that center investigators have the tools necessary to obtain immune cell populations, determine their functional properties and assess production of key mediators. Although the CSIBD research base encompasses many investigators exploring mechanisms of immune responsiveness in their laboratories, the Immunology Core offers cost-effective service while providing access to these techniques (by service and/or training) to laboratories not focused on these approaches in their primary research orientation. The specific services offered to CSIBD investigators include: 1. Flow cytometry 2. Leukocyte isolation and cell sorting 3. Multiplex cytokine assays 4. T and B lymphocyte functional assays 5. Intravital imaging of immune cells in vivo The Immunology Core assists investigators in developing assays and offers in-depth training in a number of newly developing, powerful immunologic techniques. It also provides a mechanism to support the efforts of many CSIBD Pilot/Feasibility award recipients and establish collaborations among CSIBD investigators. The Immunology Core has been highly effective in achieving its several goals of providing effective service that both facilitates research and reduces research costs, while enabling CSIBD investigators, associate investigators and personnel in their laboratories to develop and apply immunologic techniques to their research as well to foster collaborations that enhance the mission of the center.